Ask An Expert
WHOI scientist Sarah Cooley studies the impacts of ocean acidification
Sarah Cooley is a Research Associate at Woods Hole Oceanographic Institution, where she studies the socioeconomic impacts of changes in ocean chemistry.
TalkingFish: Could you share a little bit about your background? How did you become involved in marine science? What led you to study ocean acidification in particular?
Sarah Cooley: I was a chemistry major in college but wasn’t sure how I wanted to apply my knowledge. I was also a sailor, and one day it hit me that the ocean probably had chemistry and it might be a nice way to couple my interests. I participated in an NSF REU project in 1998 at the University of Delaware with Jon Sharp and I was hooked on biogeochemistry. When I entered graduate school at University of Georgia I wanted to study carbon cycling, because it was so overarching. So for my Ph.D. I studied the inorganic carbon cycling in the offshore Amazon River plume with Patricia Yager. I never did get to go up the Amazon or see any piranhas, though. The project was strictly offshore. After grad school I was self employed for a while as a science writer and editor. I was always interested in talking to nonscientists about science. Then I began my postdoc with Scott Doney at WHOI, on a project focusing on communicating the consequences of ocean acidification to the public. That work brought together my understanding of inorganic carbon cycling, my ability to write computer code, and my science writing skills, and led to my current research emphasis on using natural and social science datasets to assess how OA could affect people.
TF: Could you explain the basic mechanism of ocean acidification? What is the magnitude of the change likely to be, given current projections of carbon dioxide emissions?
SC: When excess carbon dioxide from fossil fuel burning enters the atmosphere, about 25% of it ends up dissolving in the ocean. The carbon dioxide combines with water to create carbonic acid, which lowers seawater pH. It also “sops up” some of the carbonate ions naturally present in seawater, which makes it harder for organisms like corals and shellfish to create their hard shells and skeletons. Since the beginning of the Industrial Revolution, the global ocean pH has decreased by an average of 0.1 pH units. But this decrease is accelerating. If humans continue using fossil fuels and emitting carbon dioxide at the present rate, often called the “business as usual” scenario, global computer models project an average worldwide decrease of 0.2-0.3 pH units by 2100, on top of what has already happened.
TF: A lot of the discussion on the effects of ocean acidification has focused on the shellfish industry. How will ocean acidification affect shellfish? How bad will the impacts on industry be?
SC: Ocean acidification seems to be affecting shellfish, or mollusks, in several ways. Episodic upwelling of CO2-rich water has already happened on the U.S. West Coast, creating conditions analogous to those we expect to be widespread from ocean acidification several decades from now. Wild larval oyster survival there has been nearly zero for several years running because of these ocean acidification events, and hatcheries have had to implement innovative techniques to save their product. Much of the early research on ocean acidification and organisms has focused on different types of mollusks, and it has showed that not every species behaves the same way. Some species exhibit a degree of tolerance to lower pH conditions, whereas other species experience harmful carryover effects through developmental stages or even generations after short-term exposure. Other species may have weaker shells from ocean acidification, which could alter their ability to resist predators or even physical tumbling in nature. But some species seem to respond well to selective culturing. So at the moment we can’t say with certainty how OA will affect all shellfish. But we can say that we are sure that many shellfish species will be affected, and some creative methods like selective culturing, amending water in aquaculture facilities, or raising larvae in tightly controlled conditions may be needed to preserve future harvests.
TF: Could other commercial industries could be affected by OA? How?
SC: It’s possible that other industries that depend on OA-vulnerable species could also see consequences from OA. For example, regions that depend heavily on coral reef tourism or coral-reef-based fisheries may see negative consequences from OA, and those consequences could result in decreased revenue if the quality of reef environments or fish harvests declines enough. At the same time, it’s important to recognize that changes in shellfish harvests, coral reef-associated industries, or tourism will also have trickle-down effects on other businesses and communities that depend on the OA-impacted industry. This could really amplify the overall effects of OA on human communities.
TF: Hasn’t ocean pH changed in the past? Why is this different? Will marine organisms be able to adapt?
SC: Ocean pH has indeed changed in past geological ages. But the rate of change in those situations was very, very slow — occurring over many thousands of years. Today’s change in ocean pH is extremely fast — occurring over one or two hundred years. In those past slow changes, other processes like rock weathering and seafloor mineral dissolution could help offset some of the changes in ocean chemistry that accompanied a change in pH. But today, the change is happening way too fast for these slow geological processes to counteract. It’s possible that some marine organisms will be able to tolerate these conditions, or evolve adaptations to them. But it’s also possible that today’s change is happening so fast that many organisms won’t be able to tolerate the rapid changes and the rate of evolutionary adaptation will be too slow to prevent them from going extinct.
TF: What do you think New England’s oceans will look like 50 or 100 years from now?
SC: How New England’s oceans look in the future depends completely on the choices we make in the next decades. Cutting global atmospheric CO2 emissions is the only thing that will greatly slow ocean acidification. But until that happens, New Englanders can also choose policies that avoid CO2 emissions and other types of pollution, make wise use of ocean resources like fish, and develop forward-thinking plans for using marine resources. These strategies will help maintain healthier oceans that will offer benefits to future generations as well as the current ones. For my son’s sake, I hope we do!